In this type of engine cooling device, it is arranged that not only an engine is cooled by circulating a coolant between a fluid passage formed in the internal combustion engine and a radiator but also the coolant is supplied to a heater circulation channel provided with a heater core for heating. Furthermore, in these days it is proposed that the coolant from the engine is also used for an ATF warmer or an EGR cooler.
Therefore, as described above, in order that the coolant is circulated in or supplied to each part, it becomes necessary to use a branch pipe separately and connect it to piping. Thus, there arises a problem that the piping becomes complicated and worsens engine maintenance.
Then, in order to simplify connection of the pipes described above, a coolant passage apparatus is disclosed in cited literature shown below in which the piping is directly attached to a coolant discharging outlet of the engine, a thermo valve is accommodated in the piping, and connection parts of the pipes are collected.